The affix ṭhak comes in the sense of Locative -7th case after the words āgrahāyaṇī and aśvattha ending in the 1st - Nominative Case-affix in construction and being the name of a full-moon night.,
The words सास्मिन्पौर्णमासीति of the last sutra govern this also. This debars अण् ॥ Thus आग्रहायणिको मासः 'the month called Agrahayanika' i.e. in which the moon is full in the asterism of Agrahayana. Similarly आश्वत्थिकः ॥,